personal computerPCa digital computer designed for use by only one person at a time. A typical personal computer assemblage consists of a central processing unit (CPU), which contains the computer’s arithmetic, logic, and control circuitry on an integrated circuit; two types of computer memory, main memory, such as digital random-access memory (RAM), and auxiliary memory, such as magnetic hard disks and special optical compact discs, or read-only memory (ROM) discs (CD-ROMs and DVD-ROMs); and various input/output devices, including a display screen, keyboard and mouse, modem, and printer. See also computer: History of computing.

From hobby computers to Apple

Computers small and inexpensive enough to be purchased by individuals for use in their homes first became feasible in the 1970s, when large-scale integration made it possible to construct a sufficiently powerful microprocessor on a single semiconductor chip. A small firm named MITS made the first personal computer, the Altair. This computer, which used Intel Corporation’s 8080 microprocessor, was developed in 1974. Though the Altair was popular among computer hobbyists, its commercial appeal was limited, since purchasers had to assemble the machine from a kit.

The personal computer industry truly began in 1977, when Apple Computer, Inc. (now Apple Inc.), founded by Steven P. Jobs and Stephen G. Wozniak, introduced the Apple II, one of the first pre-assembled, mass-produced personal computers. The Tandy Radio Shack TRS-80 and the Commodore Business Machines Personal Electronic Transactor (PET) were also introduced personal computers that year. These machines used eight-bit microprocessors (which process information in groups of eight bits, or binary digits, at a time) and possessed rather limited memory capacity—i.e., the ability to address a given quantity of data held in memory storage. But because personal computers were much less expensive than mainframe computers (the bigger computers typically deployed by large business, industry, and government organizations), they could be purchased by individuals, small and medium-sized businesses, and primary and secondary schools.

Of these computers, the TRS-80 dominated the market. The TRS-80 microcomputer came with four kilobytes of memory, a Z80 microprocessor, a BASIC programming language, and cassettes for data storage. To cut costs, the machine was built without the ability to type lowercase letters. Thanks to Tandy’s chain of Radio Shack stores and the breakthrough price ($399 fully assembled and tested), the machine was successful enough to persuade the company to introduce a more powerful computer two years later, the TRS-80 Model II, which could reasonably be marketed as a small-business computer.

The Apple II received a great boost in popularity when it became the host machine for VisiCalc, the first electronic spreadsheet (computerized accounting program). Other types of application software soon developed for personal computers.

IBM PC

IBM Corporation, the world’s dominant computer maker, did not enter the new market until 1981, when it introduced the IBM Personal Computer, or IBM PC. The IBM PC was only slightly faster than rival machines, but it had about 10 times their memory capacity, and it was backed by IBM’s large sales organization. The IBM PC was also the host machine for 1-2-3, an extremely popular spreadsheet introduced by the Lotus Development Corporation in 1982. The IBM PC became the world’s most popular personal computer, and both its microprocessor, the Intel 8088, and its operating system, which was adapted from Microsoft Corporation’s MS-DOS system, became industry standards. Rival machines that used Intel microprocessors and MS-DOS became known as “IBM compatibles” if they tried to compete with IBM on the basis of additional computing power or memory and “IBM clones” if they competed simply on the basis of low price.

GUI

In 1983 Apple introduced Lisa, a personal computer with a graphical user interface (GUI) to perform routine operations. A GUI is a display format that allows the user to select commands, call up files, start programs, and do other routine tasks by using a device called a mouse to point to pictorial symbols (icons) or lists of menu choices on the screen. This type of format had certain advantages over interfaces in which the user typed text- or character-based commands on a keyboard to perform routine tasks. A GUI’s windows, pull-down menus, dialog boxes, and other controlling mechanisms could be used in new programs and applications in a standardized way, so that common tasks were always performed in the same manner. The Lisa’s GUI became the basis of Apple’s Macintosh personal computer, which was introduced in 1984 and proved extremely successful. The Macintosh was particularly useful for desktop publishing because it could lay out text and graphics on the display screen as they would appear on the printed page.

The Macintosh’s graphical interface style was widely adapted by other manufacturers of personal computers and PC software. In 1985 the Microsoft Corporation introduced Microsoft Windows, a graphical user interface that gave MS-DOS-based computers many of the same capabilities of the Macintosh. Windows became the dominant operating environment for personal computers.

Faster, smaller, and more-powerful PCs

These advances in software and operating systems were matched by the development of microprocessors containing ever-greater numbers of circuits, with resulting increases in the processing speed and power of personal computers. The Intel 80386 32-bit microprocessor (introduced 1985) gave the Compaq Computer Corporation’s Compaq 386 (introduced 1986) and IBM’s PS/2 family of computers (introduced 1987) greater speed and memory capacity. Apple’s Mac II computer family made equivalent advances with microprocessors made by Motorola, Inc. The memory capacity of personal computers had increased from 64 kilobytes (64,000 characters) in the late 1970s to 100 megabytes (100 million characters) by the early ’90s to several gigabytes (billions of characters) by the early 2000s.

By 1990 some personal computers had become small enough to be completely portable. They included laptop computers, also known as notebook computers, which were about the size of a notebook, and less-powerful pocket-sized computers, known as personal digital assistants (PDAs). At the high end of the PC market, multimedia personal computers equipped with DVD players and digital sound systems allowed users to handle animated images and sound (in addition to text and still images) that were stored on high-capacity DVD-ROMs. Personal computers were increasingly interconnected with each other and with larger computers in networks for the purpose of gathering, sending, and sharing information electronically. The uses of personal computers continued to multiply as the machines became more powerful and their application software proliferated.

By 2000 more than 50 percent of all households in the United States owned a personal computer, and this penetration increased dramatically over the next few years as people in the United States (and around the world) purchased PCs to access the world of information available through the Internet.

As the 2000s progressed, the calculation and video display distinctions between mainframe computers and PCs continued to blur: PCs with multiple microprocessors became more common; microprocessors that contained more than one “core” (CPU) displaced single-core microchips in the PC market; and high-end graphic processing cards, essential for playing the latest electronic games, became standard on all but the cheapest PCs. Likewise, the processor speed, amount and speed of memory, and data-storage capacities of PCs reached or exceeded the levels of earlier supercomputers.